Fix String.prototype.split for undefined separator.

src/string.js

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 570 matching lines @@
 // ECMA-262 section 15.5.4.14
 function StringSplit(separator, limit) {
   if (IS_NULL_OR_UNDEFINED(this) && !IS_UNDETECTABLE(this)) {
     throw MakeTypeError("called_on_null_or_undefined",
                         ["String.prototype.split"]);
   }
   var subject = TO_STRING_INLINE(this);
   limit = (IS_UNDEFINED(limit)) ? 0xffffffff : TO_UINT32(limit);
 
   // ECMA-262 says that if separator is undefined, the result should
-  // be an array of size 1 containing the entire string.  SpiderMonkey
-  // and KJS have this behavior only when no separator is given.  If
-  // undefined is explicitly given, they convert it to a string and
-  // use that.  We do as SpiderMonkey and KJS.
-  if (%_ArgumentsLength() === 0) {
+  // be an array of size 1 containing the entire string.
+  if (IS_UNDEFINED(separator)) {
     return [subject];
   }
 
   var length = subject.length;
   if (!IS_REGEXP(separator)) {
     separator = TO_STRING_INLINE(separator);
 
     if (limit === 0) return [];
 
     var separator_length = separator.length;
@@ skipping 402 matching lines @@
     "fixed", StringFixed,
     "italics", StringItalics,
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
     "sup", StringSup
   ));
 }
 
 SetUpString();